The present invention relates to EDM apparatus for machining by electrical discharges an electrode workpiece by means of an electrode tool, the EDM apparatus being provided with an electrode tool holder driven by a servo motor for displacing the electrode tool as a function of the machining conditions.
In the course of machining workpieces of large dimensions, the machining of small scale details on the workpiece presents some problems which are difficult to solve, more particularly at the beginning of a machining operation when a rough pass is effected on the workpiece.
A solution consists in replacing the large dimension electrode tool by an electrode tool of smaller dimension capable of machining small details on the workpiece, following the first rough machining pass on the workpiece. However, such a method is not completely satisfactory, because the high mass inertia of the moving parts driven by the servo motor, resulting from the tool holder of large size required for supporting an electrode tool of large dimensions, reduces considerably the dynamic performance of the system, thus considerably decreasing the machining efficiency.